The water in swimming pools and spas is constantly recirculated, and fresh water is normally added only to maintain the desired volume. Although the water is usually filtered continuously to keep it free from suspended matter, it is constantly exposed to infection by pathogenic organisms (bacteria), algae and fungi. Treatment is therefore necessary to control these infections and infestations for reasons of hygiene and appearance.
A variety of sanitizing agents or systems have been used for controlling these organisms, including adding to the recreational water about 1-3 ppm chlorine, 3-5 ppm bromine, 0.1-1.0 ppm of copper and/or silver ions, 2-12 ppm alkyl, dialkyl or polymeric quaternary ammonium compounds, or 6-10 ppm poly(hexamethylene biguanide), which is referred to as PHMB. The use of PHMB for controlling algae in swimming pools is described, for example, in U.S. Pat. No. 4,014,676, and PHMB is commercially available from Zeneca Inc. as a chlorine-free swimming pool sanitizer and algistat under the trademark BAQUACIL.RTM..
However, while PHMB is a good product for killing pathogenic organisms (bactericide) in swimming pools and spas at levels of 6-10 ppm, it is generally only algistatic and fungistatic at these levels. In the swimming pool industry, even with the different sanitizers available, there is still an increase in the number of algae and fungal infestations in pools.
U.S. Pat. No. 4,253,971 of MacLeod et al. describes and claims a method of controlling pathogenic organisms, fungi and algae in water, such as swimming pool water, by using an alkali metal perborate in tablet form as a backup to PHMB to produce an algicidal effect. However, such a product has not been marketed to date, and according to that patent the perborate must be added separately from the PHMB. There is therefore still a need for more effective and more convenient sanitizing products which will have an algicidal and fungicidal effect as well as killing water-borne bacteria.